How to make a QR code reader [closed]

I want to make a QR code reader for android app. if you all have any information to create it please share with me.

What stops a QR code from working?

If you're holding your phone too close or too far away, it won't scan the code. Try holding your phone about 30 cm (1 foot) away and slowly moving it towards the QR code. Some phone cameras can't focus as well as others close up, so you may have to hold your phone a bit further away.

Can a QR code be turned off?

Note: Deactivating a QR Code is a feature of Dynamic QR Codes. It is not possible to deactivate a static QR Code as it stores the data in the QR Code itself.

Can you make a QR code invisible?

Using a special kind of ink that can only be seen in infrared light, invisible quick-response (QR) codes can now be printed onto regular documents, making them harder for counterfeiters to duplicate.

This is the most popular lib for it. It allows using the barcode scanner as intent so it doesnt require that much work either.

https://github.com/zxing/zxing/wiki/Getting-Started-Developing